Stockpiled prairiegrass-brassica hybrid mixtures tolerate repeated defoliation in autumn

Authors: Belesky, David; Ruckle, Joyce

Submitted to: Forage and Grazinglands
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/8/2006
Publication Date: 11/17/2006
Citation: Belesky, D.P., Ruckle, J.M. 2006. Stockpiled Prairiegrass-Brassica Hybrid Mixtures Tolerate Repeated Defoliation in Autumn. Online. Forage and Grazinglands doi:10.1094/FG-2006-1117-01-RS.

Interpretive Summary: Forage-based livestock production requires a reliable supply of herbage to meet goals. Stockpiling herbage, or deferring use, can help redistribute herbage availability and supplement quantity to sustain or finish livestock, depending on production objectives. Typically, autumn stockpiled herbage is harvested, with little expectation for useable regrowth. Prairiegrass and a brassica hybrid were sown in the field to determine production duration and quantity of the stockpiled mixture in autumn. Regrowth accounted for as much as 35% of the total yield in autumn when stockpiled harvests were made up to three months after planting. Stockpile and regrowth yields declined sharply thereafter. Nutritive value expressed in terms of nonstructural carbohydrates, crude protein and total digestible nutrients varied depending on year, but decreased with successive clippings or increased stockpiling duration, regardless of year. Total yield of a prairiegrass - brassica hybrid mixed stand declined in autumn, reflecting a change in the growth habit of the brassica component reflects of the stand. Mixed stands of prairiegrass - brassica hybrid can be established and clipped after the initial stockpile harvest, effectively increasing the duration of herbage production with acceptable nutritive value.

Technical Abstract: Stockpiling herbage can help redistribute nutrient availability and supplement quantity to sustain or finish livestock, depending on production objectives. Typically, autumn stockpiled herbage is harvested, with little expectation for useable regrowth. Brassicas (Brassica spp.) and prairiegrass (Bromus catharticus Vahl.) grow vigorously in autumn and tolerate defoliation. Mixed stands of prairiegrass and a brassica hybrid [B. rapa L. x B. rapa subsp. pekinensis (Lour.) Hanelt.] were established in late June of 2003 and 2004, with clipping begun 72 and 63 d after planting, respectively, to determine herbage production and nutritive value of regrowth herbage. Prairiegrass - brassica hybrid stands tolerated repeated clipping. Clipping early in autumn minimized the occurrence of weeds and increased the proportion of prairiegrass in the stand. The number of regrowth harvests decreased with increased duration of the stockpile interval, and no regrowth harvests were obtained when initial harvests were made more than 120 d after planting. Cumulative yields declined with successive harvests in 2003, but were similar until d 104 after planting and declined thereafter in 2004. Regrowth accounted for as much as 35% of the total yield in autumn when stockpiled harvests were made prior to d 104 after planting. Stockpile and regrowth yields declined sharply thereafter. Nutritive value expressed in terms of nonstructural carbohydrates, crude protein and total digestible nutrients varied depending on year, but decreased with successive clippings or increased stockpiling duration, regardless of year. Total yield and nutritive value of a prairiegrass - brassica hybrid mixed stand declined substantially about 110 d after planting, reflecting a shift in resource allocation from leaf to tuber in the brassica component of the stand.